GO:0001587

Combining with serotonin and transmitting the signal across the membrane by activation of the Gq/11 subunit of an associated cytoplasmic heterotrimeric G protein complex. The Gq/11 subunit subsequently activates phospholipase C and results in an increase in inositol triphosphate (IP3) levels. [GOC:bf, GOC:mah, PMID:18571247, PMID:18703043]